1. Field of the Invention
The present invention relates to a method of storing and transmitting image data, and more particularly to an image data format suitable for an image search using an image display.
2. Description of the Background Art
In general, original image data obtained by reading an original is stored or transmitted in the form of an image file in which the original image data follows a file header. An example of such an image file IF.sub.M is illustrated in FIG. 1, and the file header includes information for identifying the filed image.
When the amount of the original image data is very large, the original image data is often compressed through a data compression technique and then filed in the form of an image file IF.sub.N shown in FIG. 2, in order to reduce memory capacity required for storing the original image data. Image data requiring the data compression are classified into two types, one of which is that expressing an original image of large size and the other is that having a fine pixel pitch. For example, about 245 megabytes are required for storing a color image of A2 size with a pixel pitch of 160 pixels/cm, as a total capacity for color components of yellow (Y), magenta (M), cyan (C) and black (K). By means of the data compression, the required memory capacity is reduced so that such an original image data can be stored in an image memory whose capacity is not quite large.
However, even if an original image data is compressed, the amount of the original image data is still large, and a relatively large time is required for fully displaying the original image on a display device through serial access of the original image data. Therefore, when a plurality of images are serially displayed on a display device in order to find a desired original image within the plurality of images, the total time until the desired original image is found is inevitably long. Furthermore, if the respective sizes of the filed images are large, a display device of large size and an image buffer memory of large capacity must be prepared. Since a display device having a quite large size is not practical, each of the filed original images should be displayed part by part if the respective sizes of the filed original images are larger than the size of an ordinary display device.